1. Field of the Invention
The present invention relates to a rotating connection device forming a seal between two cylindrically symmetric elements rotating in relation to one another, that allows relatively substantial motions between the elements. The device according to the invention is particularly well-suited when the sections of the elements fitting into each other are relatively large.
2. Description of the Prior Art
A known method of connecting an end of a rotating tubular element 1 to an end box 2 is diagrammatically illustrated in FIG. 1. The terminal part of tube 1 is externally secured to a bellows 3 ended by an annular end plate 4. The annular plate 4, rotating with tubular element 1, is in contact, on the opposite faces thereof, with annular gaskets 5 pressed onto the plate 4 by springs 6 lodged in cavities provided in end box 2. A pipe 7, opening into box 2, communicates the inside of tube 1 with fluid injection or discharge means (not shown).
Using a bellows allows compensation for at least partly for the longitudinal or transverse motions of the end of the rotating tube in relation to the stationary end box and to substantially maintain a sealed connection. However, annular plate 4 remains subjected to certain transverse motions. The gaskets are therefore subjected to torsional stresses and quickly lose their efficiency. A risk of the gaskets sticking with the stationary part being driven in rotation may occur.
FIG. 2 illustrates another prior art layout allowing sealed connection of a stationary box 2 at the top of a tubular element 1 rotating round an axis of rotation comprises a bellows 8 externally fastened to the tubular element, an annular ring 9 fastened to the end of the bellows, provided with a radial shoulder, an annular flange 10 forming a clip connected to stationary box 2 and likely to perform a certain radial motion in relation thereto, ring-type seals or gaskets 11 interposed between the annular ring and the flange, and elastic means 12 interposed between the stationary box and the flange which presses the annular flange 10 against the seal.
The reliability of the seals with the layout of FIG. 2 is much higher because the seals work in compression when the ring undergoes radial and longitudinal displacements at the end of the bellows, as a result of possible offsets or elongations of thermal origin of the tubular element. Such a layout is suitable for connection of tubes of relatively small diameter. It is however less advantageous for tubes of relatively large diameter because of the presence of the bellows that must be sufficiently reinforced to withstand the higher twisting moment exerted thereon. As it is thicker, it loses flexibility, which has a detrimental effect on the layout efficiency for compensating for the motions of the connected elements without sealing loss.
The rotating connection device according to the invention forms a seal between an inner element and an outer element of larger diameter than the inner element, the two elements being co-axial, cylindrically symmetric and rotating in relation to one another, while allowing relatively great longitudinal and radial motions between the two elements. The moving element can be, according to the individual case, the inner element, the outer element being stationary, or conversely the outer element, the inner element being stationary.
The device of the invention finds applications in many fields. An application thereof is described hereafter, by way of non limitative example, for connection to an outer pipe of a rotating system intended for heat exchange and/or incineration of gaseous effluents containing polluting substances, such as the system described in U.S. Pat. No. 5,643,538 or EP Patent 0,757,585 filed by the assignee.
The rotating connection device comprises a shell situated in the annular space between the two elements, at least a first ring-type seal secured to the shell, placed between the outer element and the inner element, at least a second ring-type seal placed between two opposite walls of the shell and of the outer element, both perpendicular to the axis of rotation, and means for pressing the two walls against one another by means of the ring-type seal with an adjustable application force.
The device preferably comprises two ring-type seals arranged in the shell and kept spaced out in relation to one another.
According to an embodiment, the two opposite walls respectively are a rim of the outer element and of a shoulder of the tubular part, and the means for pressing the two walls against one another by means of the second ring-type seal comprises an annular plate, springs and means cooperating with said rim so as to exert an adjustable compression (by screwing for example) on the springs.
According to an embodiment, the inner element is a stationary tubular pipe and the outer element is a rotating ring with a central opening into which the tubular pipe fits.
The device can be applied for example for heat fluid transfers between an outer device and the central part of the ring gear of a heat exchange and/or incineration system comprising an enclosure in which rotates the ring containing a mass of large heat exchange surface and means for establishing a permanent radial circulation of gaseous effluents, on the one hand between effluent delivery lines and the central zone via a first limited angular sector of the ring, and on the other hand between the central zone and effluent discharge lines via a second limited angular sector of the ring.
With this mode of connection, the pipe (inner element) can withstand relatively great motions, radial as well as longitudinal, without seal deterioration or sealing loss.